Fifth coming into the game, Mainz are now serious candidates for a Europa League berth while they are level on points with fourth-placed Borussia Monchengladbach, raising the prospect of Champions League football arriving for the first time at the Coface Arena next season.

Dejected: Bayern Munich react to their defeat (Image: rex)

Blow: The result has opened up the Bundesliga title race (Image: Rex)

Arjen Robben scored the consolation for Bayern, who were beaten for only the second time all season.

Dortmund took full advantage with Adrian Ramos and Erik Durm on target as an under-strength side eased past Darmstadt 2-0.

They play host to Bayern on Saturday with only five points now between the top two with 10 games of the season to go.